1. Field of the invention
The invention relates to a data transmission system comprising a control unit, a transmitter and a receiver, said transmitter and said receiver being connected by a transmission line for the serial transmission of a series of data words in a sequence of subsequent data bits. Said control unit comprises clock means for supplying to the system a clock pulse signal, and a word select signal generator. Said word select signal generator having a first clock input for receiving said clock pulse signal and being provided with first means for generating a two level word select signal for selecting under control of a level change a data word to be transmitted. Said word select signal being supplied to said transmitter and said receiver. Said transmitter comprising storage means for temporally storing a data word to be transmitted.
2. Description of the Prior Art
A control unit to be used in such a data transmission system is for example known and realized in the device for the type CX899 of the Sony Corporation. The known device is used as control unit for an audio system. The word select signal generator generates a word select signal with a fixed period. Between two successive level changes of the word select signal a data word can be transmitted. Each time that the level of the word select signal changes another data word is selected. The fixed period of the word select signal corresponds with a fixed number of clock pulses of the clock pulse signal.
A drawback of the known system is that the period of the word select signal is fixed. Therefore only a data word with a fixed number of bits can be transmitted from the transmitter to the receiver. If the data word to be transmitted contains less bits than said fixed number, the transmitted data word has to be completed. An inefficient use of the transmission line is therefore the consequence. If the data word to be transmitted contains more bits than said fixed number, than the whole data word can not completely be transmitted.